Lighting apparatus, such as luminaries and architectural lighting, comprise an outer generally cylindrical housing that can be suspended from a lighting rig or similar. An illumination source (such as a lamp) is also provided that projects light towards a lens in the housing. The light exits the lens and illuminates the desired area. Shutters are generally placed within the lighting apparatus in the path of the light beam to alter the shape of the beam and in turn alter the shape of the projection of light on the desired area.
Shutters are usually positioned to suit different lighting scenarios. Once they have been placed in a specific positioned, it is desirable to retain them fixed in that position to prevent them from easily moving (e.g. dropping or sliding) due to gravity, normal building vibrations heat and/or accidental human intervention.